Matt Harwood Posted July 12, 2011 Share Posted July 12, 2011 Is anyone familiar with the operation of the optional electric overdrive on a Jaguar XK140? We have one for sale, and there is some speculation that it has overdrive, but I can't for the life of me figure out how it works. There's a toggle switch under the dash that looks kind of authentic, and a push/pull knob up on the firewall that looks like the one I just installed in my Cadillac, but I don't want to start trying to make it work without knowing for sure. I could make a very expensive mistake.Does anyone know how to positively identify a car with overdrive and how it operates?Thanks! Link to comment Share on other sites More sharing options...
Restorer32 Posted July 12, 2011 Share Posted July 12, 2011 The overdrive on a 140 is activated by a "willow leaf" toggle switch in the face of the dash left of the steering wheel and almost centered vertically in the dash. It is labelled Overdreive IN and OUT. That is the only control to the overdrive. Link to comment Share on other sites More sharing options...
Restorer32 Posted July 12, 2011 Share Posted July 12, 2011 Overdrive nor Overdreive, geeze. Link to comment Share on other sites More sharing options...
alsancle Posted July 12, 2011 Share Posted July 12, 2011 The overdrive switch on the dash (I believe it's clearly marked overdrive) is a glass toggle and it's made of unobtanium. If you have one you can probably get 300 bucks for it. If that switch is on the dash then the car had overdrive. Link to comment Share on other sites More sharing options...
Matt Harwood Posted July 12, 2011 Author Share Posted July 12, 2011 Is either of these switches the one? I can't go out to look at the car since it's at the warehouse on the other side of town, so I can't say if it's marked "Overdrive." Thanks so much for the quick feedback! Link to comment Share on other sites More sharing options...
Restorer32 Posted July 12, 2011 Share Posted July 12, 2011 No. The switch mounted in your dash looks like a battery cut off ? I don't believe the original is glass but I could be wrong. I'm thinking it is a hard brittle but clear plastic ? I will have to look at my 140 this evening. Hasn't been driven since 1969 and is uber original. Link to comment Share on other sites More sharing options...
alsancle Posted July 12, 2011 Share Posted July 12, 2011 Is the one hanging underneath glass? If it is the overdrive switch it's in the wrong place. Btw, Jaguar Heritage can give you the build sheet for the car. Link to comment Share on other sites More sharing options...
West Peterson Posted July 12, 2011 Share Posted July 12, 2011 No. The switch mounted in your dash looks like a battery cut off ? I don't believe the original is glass but I could be wrong. I'm thinking it is a hard brittle but clear plastic ? I will have to look at my 140 this evening. Hasn't been driven since 1969 and is uber original.JeffIs it possible the "glass" switch was replaced with a metal? Link to comment Share on other sites More sharing options...
A. Ballard 35R Posted July 12, 2011 Share Posted July 12, 2011 Perhaps the "glass" switch has something to do with the "unobtanium" material. Link to comment Share on other sites More sharing options...
Restorer32 Posted July 12, 2011 Share Posted July 12, 2011 The original "glass" switch is a toggle similar to the one under the dash but longer and more "willow leaf" like. The one now mounted on the dash looks like a turn switch but it certainly could function as an overdrive switch. Location looks correct. Simple to just look under the car at the trans and see if the overdrive is attached and if the solenoid is present. Original was a Laycock (Leycock?) unit bolted to the rear of the trans. The Jaguar Heritage Certificates are quite complete, showing all original equipment, paint, interior, top colors, list of original equipment, where and when first sold and selling dealer as well as original purchaser. Link to comment Share on other sites More sharing options...
Restorer32 Posted July 12, 2011 Share Posted July 12, 2011 Don't think I have ever seen an XK 140 that didn't have overdrive. Mine is a basic model, standard engine, disc wheels and spats, not even windshield washers but even it has OD. Link to comment Share on other sites More sharing options...
Matt Harwood Posted July 12, 2011 Author Share Posted July 12, 2011 I thought the overdrive was a rare option, with only like 800 out of the 9000 140s produced receiving it. On the other hand, I'm seeing virtually every car out there has overdrive, so perhaps it's not so rare after all. I don't know what else that switch could be for. I believe the toggle under the dash is for the fog lights, however.I have a Heritage Certificate on order, but it takes some time to get it. I'll just crawl underneath the car next time I'm over there and see for myself. Here's the car in question (oh so pretty!):Thanks for all the information!PS: West, this is DEFINITELY a car that could do without whitewalls. Too much flash! Link to comment Share on other sites More sharing options...
West Peterson Posted July 12, 2011 Share Posted July 12, 2011 Ugh!! Those tires... Link to comment Share on other sites More sharing options...
60FlatTop Posted July 12, 2011 Share Posted July 12, 2011 I have one of those switches: Link to comment Share on other sites More sharing options...
CarlLaFong Posted July 12, 2011 Share Posted July 12, 2011 I hate to be Captain Obvious here but why not look under the car? The Laycock deNormanville overdrive is easy to spot. The trans will have either a normal looking tailshaft or a roundish gizmo, with a solenoid on the side of it, instead. The gizmo it the OD Link to comment Share on other sites More sharing options...
Ivan Saxton Posted July 12, 2011 Share Posted July 12, 2011 It is a long while since I had my hands on one, but the same Laycock de Normanville overdrive was used on Humber, Standard Vanguard, and probably other English and European cars of that era. I had a 6 cylinder Vanguard ute with a four speed gearbox, and when I managed to gather a three-speed overdrive box from a wrecker, I fitted the overdrive to the four-speed box. I had to obtain a different mainshaft, which took many weeks to arrive from UK. There was a difference in overdrive ratio, which was 0.78 for the 3 speed box with wider ratios, and 0.82 for the 4 speed. This gave three close ratio top gears effectively, and the electric switch changes were very nice. The ute would really shift the scenery on the open road using the overdrive, and in those years police would not bother you unless you were driving dangerously. The mechanicals were just epicyclic like a T Ford or a slushmatic, and control was by a solenoid that disengaged a conical brake set against spring pressure. It would be nice if there was a stronger but similar unit that you could adapt to the back of a Stutz gearbox. Link to comment Share on other sites More sharing options...
West Peterson Posted July 12, 2011 Share Posted July 12, 2011 A.J.Even though this switch is made of "unobtanium," it looks like it would be a piece of cake to reproduce. I have one of those switches: Link to comment Share on other sites More sharing options...
Restorer32 Posted July 12, 2011 Share Posted July 12, 2011 I disremembered. The switch shown above IS the correct OD switch on the 140. The 150 used the willow leaf type switch that I remembered. Checked my car a bit ago and checked the parts manual. The correct switch is clear and tear drop shaped. What doesn't show in the above pics is the faceting of the end of the switch, much like a cheap diamond. Link to comment Share on other sites More sharing options...
alsancle Posted July 13, 2011 Share Posted July 13, 2011 West,If you could produce them I think there would be a market. The are very hard to come by if you need one. The picture above does not show the beveled quality of the glass very well. Link to comment Share on other sites More sharing options...
West Peterson Posted July 13, 2011 Share Posted July 13, 2011 If I had a need, I would make it. Clear plastic, a lathe, a file, and a buffing wheel. Link to comment Share on other sites More sharing options...
Restorer32 Posted July 13, 2011 Share Posted July 13, 2011 Clear plastic, mill the facets on the end first using a dividing head, then lathe, file and polish. Sounds easy doesn't it? Link to comment Share on other sites More sharing options...
alsancle Posted July 13, 2011 Share Posted July 13, 2011 Since it's oblong I'm not sure how much the lathe will help. In the end you may wish you spent the 300 bucks. Link to comment Share on other sites More sharing options...
60FlatTop Posted July 13, 2011 Share Posted July 13, 2011 I could put my switch in the Buy/Sell section for 60 bucks if it is needed.Bernie Link to comment Share on other sites More sharing options...
Restorer32 Posted July 13, 2011 Share Posted July 13, 2011 Since it's oblong I'm not sure how much the lathe will help. In the end you may wish you spent the 300 bucks.You may be right depending on what the plastic inside the switch looks like. Might have tangs or something complicated to machine. Link to comment Share on other sites More sharing options...
60FlatTop Posted July 13, 2011 Share Posted July 13, 2011 The best person to replicate a part like this might be a dentist. I remember a story about a dentist who had restored a car that was quite amateurish overall, but the dash knobs he had made were absolute jems and perfect in every way. Kind of like so many happy little teeth. Link to comment Share on other sites More sharing options...
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